The invention relates to a winding mechanism for a sun screen, for example as intended for use in an open roof construction for a vehicle, comprising a winding tube being rotatable about a central axis for winding and unwinding the sun screen and driving means for said winding tube.
In the aforesaid use in an open roof construction of a vehicle, the sun screen is capable of screening the roof opening that is formed in the open position of the open roof construction against entering sunlight. In the case of vehicle roofs which exhibit a distinct curvature in the transverse direction of the vehicle, the centre of the sun screen is positioned a considerable distance away from the roof top, so that the available headroom for occupants of the vehicle is significantly reduced.
It is an object of the present invention to provide a winding mechanism of the aforesaid type, by means of which the above drawback can be overcome in a simple yet efficient manner.
In order to accomplish that objective, the winding mechanism according to the present invention is characterized in that said central axis is curved, and in that the winding tube is flexible.
The curvature of the central axis can be so selected that the sun screen conforms to the inside contour of the roof as best as possible. In this manner, the amount of headroom that is lost in the unwound position of the sun screen is minimized. Also the winding mechanism itself occupies a minimum amount of space.
Since the winding tube must now be capable of rotation about a curved axis, the winding tube is made of a flexible material. Various plastic materials, among other materials, can be used for this purpose.
An additional advantage of such a constructional design of the winding mechanism is that the view to the front of those present in the rear of the vehicle is obstructed only minimally. In addition to that, a winding mechanism that conforms to the roof contour is aesthetically attractive.
In a preferred embodiment of the winding mechanism according to the invention, the central axis is defined by a stationary, curved inner tube, with the rotatable winding tube being mounted in bearings on said inner tube. The stationary, curved inner tube can be designed to exhibit a desired curvature adapted to that of the roof. Since the winding tube is mounted in bearings on the inner tube, the winding tube will maintain said curvature in every rotational position. The bearing between the winding tube and the inner tube furthermore provides a vibration-free positioning of the winding tube, thus ensuring an optimum operation. Furthermore, a smooth-running winding tube is obtained in this manner.
Said bearings may be spaced-apart ball bearings, for example. The number of bearings being used generally depends on the length of the winding mechanism.
Winding mechanisms of the type to which the invention relates may comprise various types of driving means. Most frequently, the driving means consist of a torsion spring engaging the winding tube for loading the winding tube to a wound position of the sun screen. With such an embodiment of the winding mechanism, it is possible according to one aspect of the invention for the inner tube to be fixed to a stationary frame of the winding mechanism with one end, at the location of a first end of the winding tube, while the other end of the inner tube terminates within the winding tube, wherein the winding tube is also mounted in bearings, at the other end thereof, on a stationary shaft which is fixed to the frame, which stationary shaft is co-axial with said central axis, and wherein said torsion spring is fitted between said stationary shaft and said winding tube.
In this manner an effective construction is obtained, wherein the torsion spring is integrated in the winding mechanism in a convenient manner. The frame may form part of a housing for the winding mechanism, or be a constructional element which is directly connected to the vehicle or the like.
The above embodiment of the winding mechanism according to the invention may furthermore be advantageously characterized in that said stationary shaft extends into the inner tube, and in that said torsion spring is accommodated in the annular space that is formed between said stationary shaft and the inner tube. In this way a compact construction is obtained.
Finally, as already briefly indicated in the foregoing, the winding mechanism may comprise a housing which accommodates the winding tube. In such a case it is preferred that the housing, too, exhibits a curvature which corresponds to the curvature of the central axis.